This invention relates to a method for gravel packing a well that penetrates an unconsolidated or poorly consolidated subterranean oil or gas reservoir.
In the production of hydrocarbons from hydrocarbon-bearing unconsolidated formations, a well is provided which extends from the surface of the earth into the unconsolidated or poorly consolidated formation. The well may be completed by employing conventional completion practices, such as running and cementing casing in the well and forming perforations through the casing and cement sheath surrounding the casing, thereby forming an open production interval which communicates with the formation.
The production of hydrocarbons from unconsolidated or poorly consolidated formations may result in the production of sand along with the hydrocarbons. Produced sand is undesirable for many reasons. It is abrasive to components within the well, such as tubing, pumps and valves, and must be removed from the produced fluids at the surface. Further, it may partially or completely clog the well, thereby making necessary an expensive workover. In addition, the sand flowing from the formation may leave therein a cavity which may result in caving the formation and collapse of the casing.
A technique commonly employed for controlling the flow of sand from an unconsolidated or poorly consolidated formation into a well involves the forming of a gravel pack in the well adjacent part or all of the unconsolidated or poorly consolidated formation exposed to the well. Thereafter, hydrocarbons are produced from the formation through the gravel pack and into the well. Gravel packs have generally been successful in mitigating the flow of sand from the formation into the well.
One of the major problems associated with gravel packing, especially in gravel packing long or inclined intervals, arises from the difficulty in completing packing the annulus between the screen and the casing for in-casing gravel packs or between the screen and the side of the hole for open hole or under-reamed gravel packs. Incomplete packing is often associated with the formation of sand "bridges" in the interval to be packed which prevent placement of sufficient sand below that bridge, for top down gravel packing, or above that bridge, for bottom up gravel packing. In accordance with this invention the problem associated with bridge formation is circumvented by permitting separate pathways for sand laden slurry to reach locations above or below the sand bridge or bridges.